$_REQUEST behavior in PHP - Step-by-Step Execution

Concept Flow - $_REQUEST behavior

Client sends HTTP request

↓

Server receives request

↓

PHP populates superglobals

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$_REQUEST combines all three

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Script accesses $_REQUEST values

When a PHP script runs, it collects data sent by the client via GET, POST, and COOKIE methods into separate arrays, then combines them into $_REQUEST for easy access.

Execution Sample

PHP

<?php
// URL: script.php?name=Alice
// POST data: age=30
// Cookie: city=Paris

print_r($_REQUEST);
?>

This code prints all input data from GET, POST, and COOKIE combined in $_REQUEST.

Execution Table

Step	Source	Data Received	$_GET	$_POST	$_COOKIE	$_REQUEST	Output
1	Client sends GET	name=Alice	{"name":"Alice"}	{}	{}	{"name":"Alice"}	{}
2	Client sends POST	age=30	{"name":"Alice"}	{"age":"30"}	{}	{"name":"Alice", "age":"30"}	{}
3	Client sends COOKIE	city=Paris	{"name":"Alice"}	{"age":"30"}	{"city":"Paris"}	{"name":"Alice", "age":"30", "city":"Paris"}	{}
4	PHP script runs	Access $_REQUEST	{"name":"Alice"}	{"age":"30"}	{"city":"Paris"}	{"name":"Alice", "age":"30", "city":"Paris"}	{}
5	Print $_REQUEST	Output combined array	{"name":"Alice"}	{"age":"30"}	{"city":"Paris"}	{"name":"Alice", "age":"30", "city":"Paris"}	Array ( [name] => Alice [age] => 30 [city] => Paris )

💡 All input sources combined into $_REQUEST and printed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
$_GET	{}	{"name":"Alice"}	{"name":"Alice"}	{"name":"Alice"}	{"name":"Alice"}
$_POST	{}	{}	{"age":"30"}	{"age":"30"}	{"age":"30"}
$_COOKIE	{}	{}	{}	{"city":"Paris"}	{"city":"Paris"}
$_REQUEST	{}	{"name":"Alice"}	{"name":"Alice", "age":"30"}	{"name":"Alice", "age":"30", "city":"Paris"}	{"name":"Alice", "age":"30", "city":"Paris"}

Key Moments - 3 Insights

Why does $_REQUEST contain data from $_GET, $_POST, and $_COOKIE all together?

Because PHP automatically merges these three superglobals into $_REQUEST, so you can access any input source from one array, as shown in execution_table rows 3 and 4.

If a key exists in both $_GET and $_POST, which value appears in $_REQUEST?

The value depends on PHP's variables_order configuration, but usually $_POST overrides $_GET in $_REQUEST. This is important to check in your PHP settings.

Can $_REQUEST be empty even if $_GET or $_POST have data?

Yes, if PHP's variables_order does not include 'G', 'P', or 'C', $_REQUEST might not be populated. See execution_table step 4 where $_REQUEST is built.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what keys does $_REQUEST contain?

A ["age", "city"]

B ["name", "age"]

C ["name", "age", "city"]

D ["name", "city"]

💡 Hint

Check the $_REQUEST column at step 3 in the execution_table.

At which step does $_POST get its value?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look at the $_POST column in execution_table rows.

If the client sends no cookies, how would $_REQUEST change?

A It would be empty

B It would not include the 'city' key

C It would only have 'city' key

D It would only have 'age' key

💡 Hint

Refer to variable_tracker for $_COOKIE and $_REQUEST values.

Concept Snapshot

$_REQUEST is a PHP superglobal array
that combines $_GET, $_POST, and $_COOKIE data.
It lets you access all input sources in one place.
Order of merging depends on PHP settings.
Use it carefully to avoid conflicts.

Full Transcript

When a PHP script runs, it receives data from the client via GET parameters, POST form data, and cookies. PHP stores these separately in $_GET, $_POST, and $_COOKIE arrays. Then, PHP merges these three arrays into one called $_REQUEST. This means you can access any input data from one array instead of checking each separately. For example, if the client sends a GET parameter 'name=Alice', a POST parameter 'age=30', and a cookie 'city=Paris', then $_REQUEST will have all three keys: 'name', 'age', and 'city'. The exact order of merging depends on PHP's configuration, but usually POST overrides GET if keys clash. This behavior is shown step-by-step in the execution table and variable tracker. Understanding $_REQUEST helps you handle user input easily but be careful with key conflicts and security.